The invention relates to a diagnostic system for a valve that can be actuated by a drive by way of a positioner and that has a sensor for detecting structure borne noise, wherein the diagnostic system determines whether diagnosis is possible and, if so, whether the valve leaks. The invention also relates to a diagnostic method, wherein the diagnostic method determines whether diagnosis of the valve is possible and, if so, whether the valve leaks.
In many areas of process engineering and power engineering, the trouble-free operation of a plant depends on the flawless functioning of the control and check valves used. To avoid costly irregular operational interruptions, any valve damage should, if at all possible, be detected early, i.e., before a valve failure can cause the plant to be shut down. Defective valve seats, for example, cause leakage flows that emit broadband noise. Detecting and evaluating the noise emission of a valve can thus be used for early detection of valve damage. Since valve faults can lead to damage and expensive follow-up costs, a diagnosis, possibly with automatic detection and programmable evaluation of the faults, is highly useful. Statistical evaluations of the diagnostic data can be used to optimize the maintenance processes to ensure a timely replacement of a faulty valve, and to qualitatively evaluate and classify the valve manufacturers, or to evaluate the suitability of specific valves for different process types.
German Laid Open Publication DE 199 24 377 A1 discloses a diagnostic system for a valve that can be actuated by a positioner using a drive. This system has a device for recording, storing and evaluating structure-borne noise spectra measured on the valve. To enable a particularly reliable valve diagnosis, the structure-borne noise spectra measured for a slightly open intact valve can be stored in the recording, storing and evaluating device. For the diagnosis, a structure-borne noise spectrum measured for the closed valve is compared with the stored spectrum, and the similarity of the spectra is used to determine whether the valve leaks.
A further diagnostic system for a valve is known from German Laid Open Publication DE 199 47 129 A1.